Basics on the use of acid-sensing ion channels' inhibitors as therapeutics

Since the discovery of acid-sensing ion channels in 1997, their importance in the health of neurons and other non-neuronal cells has gained significant importance. Acid-sensing ion channels play important roles in mediating pain sensation during diseases such as stroke, inflammation, arthritis, cancer, and recently migraine. More interestingly, acid-sensing ion channels may explain the sex differences in pain between males and females. Also, the ability of acid-sensing ion channel blockers to exert neuroprotective effects in a number of neurodegenerative diseases has added a new dimension to their therapeutic value. The current failure rate of ～45% of new drugs(due to toxicity issues) and saving of up to 7 years in the life span of drug approval makes drug repurposing a high priority. If acid-sensing ion channels' blockers undergo what is known as "drug repurposing", there is a great potential to bring them as medications with known safety profiles to new patient populations. However, the route of administration remains a big challenge due to their poor penetration of the blood brain and retinal barriers. In this review, the promise of using acid-sensing ion channel blockers as neuroprotective drugs is discussed.     

Comparing the results of Pap smear and Direct Visual Inspection (DVI) with 5% acetic acid in cervical cancer screening

Background:

Cervical cancer is the most second common cancer among Iranian women. This study was carried out to compare the results of Pap smear method and Direct Visual Inspection (DVI) with 5% acetic acid in cervical cancer screening in Tabriz, Iran.

Material and Methods:

This cross-sectional study was carried out in Alzahra Therapeutic-Educational Centre, Tabriz, Iran in 2013 on 1000 women. First, Pap smear was done for all women, and then the cervix exposed with 5% acetic acid by cotton swab for 30 seconds and observed under adequate light. At the end, women with abnormal results in Pap smear or DVI method were referred to colposcopy and biopsy. Test''s sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), LR+, LR- and confidence interval (CI) were determined (P < 0.05).

Results:

Nine-hundred and seventy-four (94.7%) cases were normal and had no abnormal findings and 26 (2.6%) participants had positive results in Pap smear or DVI test. Twelve women had abnormal Pap smear (nine women with atypical squamous cells of undetermined significance, ASCUS, three women with dysplasia, atypical endocervical, and low-grade squamous intraepithelial lesion, LSIL results) and 14 women had positive DVI (four women with human papillomavirus, HPV or koilocyte,) and one women with abnormality in both method had carcinoma in biopsy that referred to oncologist. In this study the sensitivity, specificity, PPV and NPV for DVI were 71.4%, 50%, 35.7%, and 81.8% respectively in comparison with 14.3%, 50%, 10%, and 60% for Pap smear.

Conclusion:

As the DVI method has higher sensitivity and positive predictive value than Pap smear, it could be used as a useful method beside the Pap smear.     

Stress-induced changes in neuronal Aquaporin-9 (AQP9) in a retinal ganglion cell-line.

The water channel, Aquaporin-9 (AQP9) is enriched in selected neuronal populations and is unique its ability to act as a lactate-glycerol channel supplying neurons with alternative fuel under ischaemic conditions. AQP9 was detected in RGC-5 cells, a retinal ganglion cell-line, primary RGCs, and retina by Western blotting, real-time PCR (RT-PCR) and immunohistochemistry. RGC-5 cells subjected to a hypotonic stress increased their cell volume that was blocked by known inhibitor of AQP9 (phloretin (40 microM)). RGC-5 cells subjected to hypoxia, showed an up-regulation in AQP9 expression as judged by Western blotting and RT-PCR. Similarly, hypotonic shock (50%) increased AQP9 expression as determined by RT-PCR. AQP9 is involved in energy balance as a glycerol-lactate channel and also appears to regulate cell volume in retinal ganglion neurons. This water channel may play a key role in retinal ganglion pathology.     

Pentylenetetrazole-induced inhibition of recombinant gamma-aminobutyric acid type A (GABA(A)) receptors: mechanism and site of action

Pentylenetetrazole (PTZ) is a central nervous system convulsant that is thought, based on binding studies, to act at the picrotoxin (PTX) site of the gamma-aminobutyric acid type A (GABA(A)) receptor. In the present study, we have investigated the mechanism and site of action of PTZ in recombinant GABA(A) receptors. In rat alpha 1 beta 2 gamma 2 receptors, PTZ inhibited GABA-activated Cl(-) current in a concentration-dependent, voltage-independent manner, with an IC(50) of 0.62 +/- 0.13 mM. The mechanism of inhibition appeared competitive with respect to GABA in both rat and human alpha 1 beta 2 gamma 2 receptors. Varying subunit configuration (change or lack of alpha subunit isoform or lack of gamma 2 subunit) had modest effects on PTZ-induced inhibition, as evidenced by comparable IC(50) values (0.6-2.2 mM) in all receptor configurations tested. This contrasts with PTX and other PTX-site ligands, which have greater affinity in receptors lacking an alpha subunit. Using a one-site model for PTZ interaction with alpha 1 beta 2 gamma 2 receptors, the association rate (k(+1)) was found to be 1.14 x 10(3) M(-1) s(-1) and the dissociation rate (k(-1)) was 0.476 s(-1), producing a functional k(d) of 0.418 mM. PTZ could only gain access to its binding site extracellularly. Single-channel recordings demonstrated that PTZ decreased open probability by increasing the duration of closed states but had no effect on single-channel conductance or open state duration. alpha-Isopropyl-alpha-methyl-gamma-butyrolactone, a compound known to antagonize effects of PTX, also diminished the effects of PTZ. Taken together, our results indicate that pentylenetetrazole and picrotoxin interact with overlapping but distinct domains of the GABA(A) receptor.     

Vitamin D status of children receiving chronic dialysis

Background

Patients receiving chronic dialysis therapy are presumed to be at risk for 25(OH) D₃ deficiency, but little information is available on its prevalence, manifestations of deficiency, and the impact of ergocalciferol supplementation.

Methods

A single-center, retrospective study of 51 prevalent pediatric patients on hemodialysis or peritoneal dialysis was conducted to address these issues.

Results

Forty of 51 (78.4 %) patients had low (<30 ng/ml) 25(OH) D₃ levels. Of these, 2 % had values?12 years, non-Caucasian race and?>?12-month duration of dialysis were significantly associated with low 25(OH) D₃ levels (p?=?0.006, p?=?0.05, and p?=?0.04, respectively). Twenty-three of the 40 patients deficient in 25(OH) D₃ received repletion therapy with ergocalciferol and had a follow-up level at an average of 2 months following completion of a single course of therapy; 14 (60 %) of the levels were normal. Mean baseline intact parathyroid hormone (iPTH) for patients with 25(OH) D₃ levels?≤?30 was 478.68?±?474.01 pg/ml and treatment with ergocalciferol was not associated with a significant decrease in the mean iPTH value (p?=?0.45).

Conclusions

We conclude that low 25(OH) D₃ levels are common in pediatric patients receiving dialysis and require attention in accordance with current practice guidelines.